I spent 2 nights at the ANA & 5 nights at the strings in October on point breaks. Stays were similar to the above 2 posts.

I was upgraded to superior at the ANA, the welcome fruit basket was excellent - a huge bunch of gigantic sweet grapes (tasted like a fine sweet wine), apple-pear, plums & chocolates, plus 2 bottles of water refills each day. Also a luggage tag. First class treatment throughout. Lots of storage space in the room - i.e. plenty of drawers. The grapes alone were selling for about $20 in the stores.

The Strings - my welcome was "no upgrade on reward stay" - I did not even ask. Welcome gift was a tiny cup containing maybe 3 small peices of pineapple and 5 or 6 blueberries plus the travel cup. 2 bottles of water for the entire stay. Treatment was firstclass, though I did not receive my wake-up call one morning. Lack of storage space here, only 2 small drawers, so not really set-up for a stay of more than 2 nights, definitely not 5 nights.

I would stay at both locations again, my choice depending on what my schedule is in Tokyo. The Strings has the advantage of being next to Shinagawa JR station, so it is very easy to/from Narita by JR. The ANA requires a walk from the subway station with steps only in a few locations, which can be nuisance if you have a lot of luggage.